Common lens transmitter for motion compensated illumination

Abstract

A laser transmission apparatus utilizing multiple laser beams and beam paths with a diverger lens to provide an illumination pattern that can compensate for lateral movement of the platform during shearography is provided. Further, this optical setup requires no moving parts and does not reduce power of the laser beams as they move through the individual components thereof. From the perspective of the surface being scanned or inspected, the present disclosure may provide two laser images of a single surface that appear to be identical despite the fact that they were taken from two different spatial positions of the moving platform.

The invention claimed is: 
     
       1. An optical transmitter for shearography comprising:
 a first beam generator wherein the first beam generator is a laser beam generator that generates a first laser beam along a first beam path through the optical transmitter; 
 a second beam generator wherein the second beam generator is a laser beam generator that generates a second laser beam along a second beam path, different than and not overlapping with the first beam path, through the optical transmitter; and 
 a diverger lens within both of the first and second beam paths, wherein the first beam and the second beam travel through an identical point on the diverger lens and the diverger lens produces a beam spread illumination pattern; 
 a receiver configured to detect reflections of the beam spread illumination pattern generated by the first and second beams after traveling through the diverger lens; and 
 a processor configured identify non-uniform movement of a reflecting surface by comparing, overlaying, or comparing and overlaying reflection data from the receiver. 
 
     
     
       2. The optical transmitter of  claim 1  wherein the diverger lens is spherical and is positioned at an intersection of the first and second beam paths. 
     
     
       3. The optical transmitter of  claim 2  further comprising:
 a first shaping optic within the first beam path; and 
 a second shaping optic within the second beam path. 
 
     
     
       4. The optical transmitter of  claim 3  wherein the first shaping optic further comprises:
 a first lens pair within the first beam path between the first beam generator and the diverger lens, wherein the first lens pair is operable to independently determine the X and Y divergence of the first beam. 
 
     
     
       5. The optical transmitter of  claim 3  wherein the second shaping optic further comprises:
 a second lens pair within the second beam path between the second beam generator and the diverger lens, wherein the second lens pair is operable to independently determine the X and Y divergence of the second beam. 
 
     
     
       6. The optical transmitter of  claim 2  wherein each of the first beam path and the second beam path are oriented at an angle relative to the other of the first beam path and the second beam path. 
     
     
       7. The optical transmitter of  claim 1  wherein the optical transmitter is carried by a moving platform, wherein the beam spread from the diverger lens appears to originate from a substantially same spatial point despite having been generated from two separate locations due to the moving platform. 
     
     
       8. The optical transmitter of  claim 7  wherein the moving platform further comprises:
 one of a rotary-winged aircraft, fixed wing aircraft, drone, and lighter than air aircraft. 
 
     
     
       9. The optical transmitter of  claim 1  wherein the first beam generator and second beam generator are the same beam generator that is operable to generate a single beam and further comprises:
 a plurality of optical components operable to direct the single beam down a first beam path and a second beam path separate from the first beam path. 
 
     
     
       10. The optical transmitter of  claim 9  wherein the plurality of optical components further comprise:
 at least one high speed switching optic to change the direction of the single beam from the first path to the second path. 
 
     
     
       11. The optical transmitter of  claim 9  wherein the plurality of optical components further comprise:
 a beam splitter operable to split the single beam into the first path and the second path. 
 
     
     
       12. A method of performing shearography comprising:
 generating a first laser beam along a first beam path from a first beam generator carried by a platform; 
 directing the first laser beam through a diverger lens towards a target surface; 
 moving the platform from a first position to a second position; 
 generating a second laser beam along a second beam path, different than and not overlapping with the first beam path, from a second beam generator carried by the platform; and 
 directing the second laser beam through an identical point as the first laser beam on the diverger lens towards the target surface for a shearography measurement, wherein the diverger lens produces a beam spread from the first laser beam and the second laser beam that appears to originate from a substantially same spatial point despite having been generated from two separate locations. 
 
     
     
       13. The method of  claim 12  further comprising:
 applying a stressor to the target surface after directing the first laser beam through the diverger and prior to generating the second laser beam. 
 
     
     
       14. The method of  claim 13  wherein applying the stressor to the target surface further comprises:
 applying one of a mechanical stressor and an acoustic stressor to the target surface. 
 
     
     
       15. The method of  claim 13  further comprising:
 receiving each of the first and second laser beams as they reflect off of the target surface. 
 
     
     
       16. The method of  claim 15  wherein receiving each of the first and second laser beams further comprises:
 receiving the first laser beam reflection prior to applying the stressor; and 
 receiving the second laser beam reflection after applying the stressor. 
 
     
     
       17. The method of  claim 16  further comprising:
 creating a first interference pattern from the received first laser beam reflection and second interference pattern from the received second laser beam reflection via a processor. 
 
     
     
       18. The method of  claim 17  further comprising:
 comparing the first interference pattern to the second interference pattern to determine if a change to the target surface has occurred. 
 
     
     
       19. The method of  claim 18  further comprising:
 communicating a result of the comparison between the first and second interference patterns to an operator of the platform. 
 
     
     
       20. The method of  claim 19  wherein communicating the result of the comparison further comprises:
 communicating the result of the comparison between the first and second interference patterns to an operator of the platform only if a change is detected in the target surface.